For example, JP-A-2007-6560 discloses a conventional rotation angle detection device configured to detect the rotation angle of a brushed direct-current motor. Such a brushed direct-current motor includes a rotor including a stator, which has multiple magnetic poles, and an armature winding accommodated in multiple slots, a commutator connected with the armature winding, and a pair of brushes for supplying electricity from an external power source to the armature winding. The commutator is mounted on an end of a shaft of the direct-current motor for detection of the rotation angle. Electric conduction among the two brushes and the commutator is repeatedly made and removed with rotation of the shaft to cause pulse signals. The rotation angle detection device counts the pulse signals thereby to detect the rotation angle of the direct-current motor.
In the rotation angle detection device disclosed in JP-A-2007-6560, an end of the shaft of the direct-current motor is equipped with a sensor separately from the stator and the rotor. Therefore, the rotation angle detection device may be enlarged. In addition, the rotation angle detection device cannot detect the rotative direction of the motor. Therefore, when, for example, an external force is applied to the direct-current motor to rotate the direct-current motor in the right of reverse direction, it is hard to detect the rotation angle of the direct-current motor correctly.